In this article, we’ll go over the Top 26 Programming Interview Questions for 2025.
When you’re preparing for a job interview, programming interview questions can be tough. These questions test your coding skills and how you solve problems.
Whether you’re aiming for a tech role or a developer job, you’ll likely face these kinds of questions. So, let’s take a look at some common programming questions and tips to help you do your best.
With the right prep, you’ll feel ready to take on any challenge.
Top 20 Programming Interview Questions
Here is the list of top Programming Interview Questions you should know:
Basic Programming Questions
1. What is the difference between a stack and a queue?
Ans: A stack follows the “Last In, First Out” (LIFO) principle, meaning that the last element added to the stack is the first one to be removed. You can think of it as a stack of books, with the last book placed on top being the first to be taken off.
In contrast, a queue follows the “First In, First Out” (FIFO) principle, where the first element added is the first one to be removed, similar to a line of people waiting for service The first person in line is the first to be served.
2. What is the difference between a list and a tuple in Python?
Ans: In Python, a list is a mutable data structure, meaning you can modify its contents after it’s created. You can add, remove, or change elements in a list. For example, you can change the value of an element at a specific index.
On the other hand, a tuple is immutable, meaning that once it is created, its contents cannot be changed. Tuples are useful for storing data that should not be altered, ensuring that the integrity of the data is preserved.
3. Explain the concept of recursion with an example.
Recursion is a technique where a function calls itself to solve smaller instances of the same problem. This continues until a base case is reached, which is a condition that stops the recursion.
A classic example of recursion is the calculation of a factorial, where the factorial of n (denoted as n!) is n * (n-1)!. The base case is when n = 0, which equals 1. This allows the function to compute the factorial by calling itself with smaller and smaller values of n.
4. What is the difference between==andisin Python?
Ans: The == operator is used to compare values. It checks whether the values stored in two variables are the same. For example, if two lists have the same elements, == will return True. In contrast, the is operator checks whether two variables refer to the same object in memory. Two variables can have the same value but still refer to different objects in memory, which is will detect.
5. How do you handle errors in programming?
In most programming languages, errors or exceptions are handled using constructs like try-except blocks (in Python).
The idea is to wrap potentially problematic code in a try block, and if an error occurs, the program jumps to the except block to handle the error without crashing.
This helps maintain the stability of the program and can allow you to provide user-friendly error messages or recover from certain types of errors.
6. What is an array, and how is it different from a linked list?
Ans: An array is a fixed-size data structure in which elements are stored in contiguous memory locations. This allows for constant-time access to elements by their index.
However, arrays have a fixed size, meaning you cannot add more elements once the array is full without resizing it. In contrast, a linked list is a dynamic data structure where each element (node) points to the next element, allowing the list to grow or shrink in size without needing contiguous memory. However, accessing elements in a linked list requires traversing the list, making it slower than an array.
6. What is the purpose of thebreakandcontinueStatements in loops?
Ans: The break statement is used to terminate a loop early, before it has completed all iterations. This is useful when you want to stop processing once a certain condition is met.
On the other hand, the continue statement is used to skip the current iteration of the loop and continue with the next iteration. While break exits the loop completely, continue allows the loop to continue but skips the remaining code for the current iteration.
7. What are the different types of operators in programming?
Ans: There are several types of operators in programming, each serving a different purpose:
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Arithmetic operators (e.g.,
+,-,*,/) perform mathematical operations on numbers. -
Logical operators (e.g.,
and,or,not) are used to combine conditional statements. -
Relational operators (e.g.,
==,<,>) compare values and return a Boolean result. -
Assignment operators (e.g.,
=,+=,-=) assign values to variables.
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Intermediate Programming Questions
8. What is a hash table and how does it work?
Ans: A hash table is a data structure that stores key-value pairs. It uses a hash function to compute an index in an array, where the value associated with a key can be found.
When you want to retrieve or insert a value, the hash function ensures that it is placed in the correct location, providing fast lookups. In case of collisions (where two keys hash to the same index), techniques like chaining or open addressing are used to handle them.
9. Explain what a binary search is and when you should use it.
Ans: Binary search is an efficient algorithm for finding an element in a sorted array. It works by repeatedly dividing the search interval in half, comparing the middle element with the target.
If the target is smaller, the search continues in the left half; if it’s larger, the search continues in the right half.
Binary search is much faster than a linear search because it reduces the number of comparisons needed, with a time complexity of O(log n).
10. What are the advantages of using object-oriented programming (OOP)?
Ans: Object-Oriented Programming (OOP) promotes code modularity, reusability, and maintenance by organizing code into classes and objects.
This approach allows for better structure in code, where each object represents a real-world entity and can have its own attributes and methods.
OOP encourages the use of inheritance, polymorphism, and encapsulation, which makes code easier to maintain, extend, and reuse across different projects.
11. What is the time complexity of accessing an element in an array?
Ans: Accessing an element by index in an array is an O(1) operation, meaning it takes constant time regardless of the size of the array. This is because arrays store elements in contiguous memory locations, allowing for direct access to any element using its index.
Advanced Programming Questions
12. What is the time complexity of quicksort, and why is it efficient?
Ans: Quicksort is a divide-and-conquer algorithm with an average time complexity of O(n log n). It works by selecting a pivot element and partitioning the array into two smaller subarrays: one with elements smaller than the pivot and one with elements larger.
The subarrays are then recursively sorted. Quicksort is efficient because it quickly narrows down the search space, making fewer comparisons than other sorting algorithms like bubble sort or insertion sort.
13. Explain the concept of a graph and the types of graphs you know.
Ans: A graph is a collection of nodes (or vertices) and edges that connect pairs of nodes. There are several types of graphs:
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Directed graphs (or digraphs) where edges have a direction, i.e., they point from one node to another.
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Undirected graphs where edges have no direction.
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Weighted graphs where edges have associated weights or costs.
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Unweighted graphs where all edges are equal.
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Cyclic graphs that contain at least one cycle (a path that starts and ends at the same node).
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Acyclic graphs that do not contain any cycles.
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14. What is a cache, and how does it improve performance?
Ans: A cache is a temporary storage area that stores frequently accessed data in a faster storage medium, such as RAM or an SSD. The purpose of caching is to reduce the time it takes to retrieve data. By keeping frequently used data in the cache, you avoid the need to repeatedly fetch or compute the same data, improving the performance and responsiveness of a system.
15. Explain the concept of Big O notation. What’s the time complexity of a nested loop?
Ans: Big O notation is a mathematical representation that describes the upper bound of an algorithm’s runtime as the input size grows. It helps classify algorithms based on how they scale with larger inputs. The time complexity of a nested loop is typically O(n²), where n is the number of iterations in the outer loop. This is because the inner loop runs n times for each iteration of the outer loop.
16. What is a binary tree, and what is the difference between a binary tree and a binary search tree (BST)?
Ans: A binary tree is a tree data structure where each node has at most two children (referred to as the left and right children). A binary search tree (BST) is a special type of binary tree where the left child is smaller than the parent node, and the right child is larger than the parent node. This property makes BSTs useful for efficient searching and sorting operations.
17. What is the difference between an if statement and a switch-case statement?
Ans: An if statement is used to evaluate one or more conditions and execute code based on whether those conditions are true or false. It supports complex conditions using logical operators like AND and OR.
A switch-case statement (available in some languages like C, Java, and JavaScript) is used to handle multiple possible values of a single variable. It’s often used when you have a fixed number of options to choose from.
18: What is the purpose of the return keyword in functions?
Ans: The return keyword is used in a function to send the result or output back to the calling code. It allows the function to provide a result that can be used or stored elsewhere in the program, and it ends the function’s execution.
19. What is a comment in code, and why is it important?
Ans: A comment is a line of text in the program that is ignored by the computer but is meant to provide explanations or clarifications for humans reading the code. Comments are important for improving code readability, helping other developers (or future you) understand what the code is doing.
20. What is the difference between a function and a method?
Ans: A function is a block of reusable code that performs a specific task and can be called with parameters to return a result. A method is similar to a function but is associated with an object or class. It typically operates on the data within that object and is called on that object.
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Conclusion: Programming Interview Questions
In conclusion, programming interview questions are key to understanding a candidate’s technical skills, problem-solving approach, and ability to think critically.
By asking or answering the questions, you not only assess their knowledge but also get a sense of how they approach challenges and learn new technologies.
This helps you identify the most qualified candidates who can contribute effectively to your team. Overall, these questions are vital in selecting the right fit for the job.
